Uniform display of book/ author names in the Canvas

[yannickmartinlmu]

Currently there are two distinct ways labels are presented:

• On Hover as a Tooltip
• Below each blot in a small box.

They are not visually identical and also don't get displayed mutually exclusive.
When zoomed in, Hover is disabled. When zoomed out, the boxes below each blot are disabled.
However there exist zoom levels where both are active.
Additionally, the boxes below each blot appear very early when there are still many blots on screen, so it becomes visually cluttered.

Change the presentation of the labels to be more consistent.